The head on the 10 cent is a generic "Laotian maiden".
The triple-headed elephant on the 20 cent is the Hindu divinity Erawan, and was the national emblem of the Kingdom (see the flag and coat of arms on the Wikipedia page I linked to above). Although Laos is Buddhist rather than Hindu, the elephant is native to the region and was long a symbol of royalty. A very similar elephant symbol is still used in neighbouring Thailand.
The book on the 50 cent symbolizes the tripitaka, the recorded teachings of Buddha - the Buddhist sacred writings.
The leaf-like patteron on the reverses is intended to be a lotus flower.
Western colonial powers often struck colonial coins for their native subjects, especially low-denomination ones, with holes in them. The theory was that most versions of non-western clothing don't have pockets, so holed coins allow the coins to be strung on strings and carried around the neck. Perhaps not surprisingly, this somewhat patronising attitude was rarely followed through once the various countries attained independence. These are the only holed coins issued for Laos.
I do not know if the holes on these particular coins were a last-minute addition or were always intended as part of the design, but the entire mintage (2, 3 and 1.4 million respectively) was holed.